Yilmaz Yaşar, Kaya Demet, Pekcan Onder
Department of Physics, Istanbul Technical University, Maslak, 80626 Istanbul, Turkey.
Eur Phys J E Soft Matter. 2004 Sep;15(1):19-25. doi: 10.1140/epje/i2003-10156-9.
Recent observations (Eur. Phys. J. E 9, 135 (2002)) showed that the vitrification process, which sets in during the linear bulk methyl methacrylate (MMA) polymerization carried out below glass transition temperatures, can be modelled by static percolation picture. To generalize this observation for different kind of bulk linear or crosslinked polymers not enough data are present in the literature. To cover partly this deficit we studied the glass transition of MMA and styrene (Sty) crosslinking copolymerization in varying ratios of MMA and Sty. Both the fluorescence intensity I and the lifetime tau of pyrene (Py) used as a nanosecond in situ fluoroprobe were monitored during the gelation time. Both I and tau increase dramatically as a result of the reduced mobility of the probes trapped in the "glassy" regions, appearing near the glass transition point. The average size of the glassy regions just below, and the strength of the infinite network formed upon the connection of the glassy regions above the glass transition point tg obey power law relations. The data around tg were interpreted on the basis of the percolation theory and we observed that the corresponding exponents gamma and beta give static percolation values independent of the polymer composition.
最近的观察结果（《欧洲物理杂志E》9，135（2002））表明，在低于玻璃化转变温度下进行的线性本体甲基丙烯酸甲酯（MMA）聚合过程中开始的玻璃化过程，可以用静态渗流图像来模拟。对于不同种类的本体线性或交联聚合物，为了推广这一观察结果，文献中没有足够的数据。为了部分弥补这一不足，我们研究了不同比例的MMA和苯乙烯（Sty）交联共聚的玻璃化转变。在凝胶化时间内，监测了用作纳秒原位荧光探针的芘（Py）的荧光强度I和寿命τ。由于被困在“玻璃态”区域的探针迁移率降低，I和τ都显著增加，这些区域出现在玻璃化转变点附近。刚好低于玻璃化转变温度时玻璃态区域的平均尺寸，以及在高于玻璃化转变温度tg时玻璃态区域连接形成的无限网络的强度，服从幂律关系。基于渗流理论对tg附近的数据进行了解释，我们观察到相应的指数γ和β给出了与聚合物组成无关的静态渗流值。
